One type of electrical connector commonly is called an "edgecard" connector in that it includes an elongated housing having an elongated slot for receiving, edgewise, a printed circuit board. The connector includes a plurality of terminals mounted along one or both sides of the slot for making electrical contact with circuit traces adjacent the edge of the circuit board.
The terminals which often are used in edgecard connectors are press-fit terminals having stamped and formed spring arm contacts for mechanically and electrically engaging the circuit traces on the printed circuit board. A problem which consistently surfaces in the design of such edgecard connectors is the dilemma of providing high normal forces which are associated with undesirably high insertion forces of the board into the connector. In order to provide satisfactory mating between the board and the spring arm contacts, a sufficient normal force must be created to assure the desired electrical contact. A typical edgecard connector includes parallel opposing rows of terminals having spring arm contacts extending toward each other and defining convex contact engaging surfaces engageable with the circuit board. The spring arms act as cantilever beams, so that when a board is slidably inserted therebetween, the ends of the spring arm contacts are forced laterally apart. Typically, the higher the normal force provided, the greater the insertion force.
One solution to the above problem of balancing high normal contact forces with undesirable high insertion forces has been to "preload" the terminals. In other words, when the terminals are press-fit into respective passages in the connector housing, the cantilevered spring arms are preloaded or "cocked" against their resiliency and held or preloaded in that condition behind retaining shoulders of the connector housing.
While preloaded terminals are effective to solve certain problems, as described above, they have the potential of creating more serious problems, particularly when relatively long connector housings are exposed to relatively high processing temperatures. Specifically, an edgecard connector often interconnects a first printed circuit board received edgewise in the connector, as described above, with a second printed circuit board by soldering processes which require the application of heat. When an elongated connector housing is exposed to high heat, the plastic material of the housing may soften, and the preloaded terminals apply pressure to the housing which tends to collapse the softened housing along the boardreceiving slot. The housings could be fabricated of materials which do not collapse under the forces of the preloaded terminals, but such materials often are cost prohibitive.
In order to solve the myriad of problems outlined above, attempts have been made to control the inserted location of the terminals and, thereby, avoid the use of terminals having preloaded spring contact portions. For instance, it has been proposed to provide each terminal with a retention portion that is press-fit in a retention section of a respective terminal-receiving passage in the connector housing. In one proposal, the retention section of the passage essentially grips the edges of the retention portion of the terminal as the terminal is inserted into its passage. The retention section of the passage may be tapered to guide the terminal during insertion as the retention section grips the edges of the terminal. When the terminal is fully inserted, a narrower area of the tapered retention section fully grips the edges of the retention portion by a press-fit. In some applications, problems have been encountered in controlling the insertion location of the terminals.
Another solution has been to use additional insertion tooling as a back-up to the retention portion of the terminal to properly guide the terminal during insertion and eventually locate the fully inserted terminal. Once the terminal is fully inserted, the additional guiding tooling is removed. However, not only does the connector housing have to be designed to accommodate the additional guiding and supporting tooling, but the tooling adds expenses in both the tooling, itself, as well as the processing equipment used in conjunction with the tooling.
The present invention is direction to solving these problems by providing means directly on the connector housing for guiding, locating and supporting the terminals within the connector housing.